This research aims to provide information on the interaction of ions and certain drugs with the excitable membrane of giant axons. These efforts may discover some elements of the structure of the ionic permeation pathways and may aid in determining how local anesthetics, convulsants and anti-arrhythmic drugs act on these cells. Information on the structure of the ionic pathways can come from measurements of the unidirectional fluxes of Na and K ions in voltage-clamped axons and how these fluxes are influenced by the presence of other permeant and impermeant ions. Drug interactions will be studied using the relatively new technique of electrical current fluctuation (noise) analysis. This technique allows the measurement of the unit conductance of single channels; the effects of certain drugs on this single channel conductance can be studied. The results of these observations may lead to a better understanding of the structure of excitable cells and may lead to the design of specific neuropharmacological agents that would act on the membranes at designated sites in predictable ways, with a minimum of side effects.